For the next few years, a dramatic increase in oncoses and tumor-related cases of death is expected worldwide. In 2001, worldwide approximately 10 million people were suffering from cancer and over 6 million people died from this disease. The development of tumours is a fundamental disease of higher organisms in the plant kingdom, in the animal kingdom and in humans. The generally recognized multistep model of carcinogenesis assumes that as a result of accumulation of a number of mutations in an individual cell this is so modified in its proliferation and differentiation behaviour that finally, via benign intermediate stages, a malignant state with metastasis is reached.
The term cancer or tumor conceals a clinical picture with more than 200 various individual diseases. Oncoses can proceed in a benign or malignant manner. The most important tumours are those of the lung, the breast, the stomach, the neck of the uterus, the prostate, the head and neck, the large and small intestine, the liver and the blood system. There are great differences with respect to course, prognosis and therapy behaviour. More than the 90% of the cases recognized relate to solid tumours, which in particular in the advanced stage or on metastasis are treatable with difficulty or are untreatable. The three pillars of cancer control are still surgical removal, irradiation and chemotherapy. In spite of great advances it has not yet been possible to develop medicaments which bring about a marked prolongation of the survival time or even a complete cure in the widespread solid tumours. It is therefore meaningful to invent novel medicaments for the control of cancer.
Natural substances are an important source for novel lead structures in pharmaceutical research and are in some cases also directly suitable for the development of a novel medicament (Shu Y, J. Nat. Prod. 1998, 61: 1053-1071). It is known that many natural substances possess strongly cytotoxic action (Ram V J et al., Drug News Perspect 2001, 14(8): 465-482).
It is known that natural substances of the group consisting of the disorazoles are isolated from the bacterium of the strain Sorangium cellulosum So ce12 (Jansen R et al., Liebigs Ann. Chem. 1994, (8): 759-773).
In total, 29 disorazoles have been isolated and characterized physicochemically. For the disorazole A1, it was reported that it possesses an antiproliferative action in cell models (Irschik H et al., J. Antibiotics 1995, 48(1): 31-35; Elnakady Y A, Dissertation 2001, Technische Universität Carolo-Wilhelmina zu Braunschweig). However, use for the treatment of oncoses was neither disclosed nor suggested. A biological investigation of the other disorazoles was not carried out.
WO 2004/024149 reports that in particular disorazoles E1 and D1 possess cytotoxic action on various human tumor cell lines. In nano- and picomolar concentrations, the division, inter alia, of ovarian carcinoma, prostate carcinoma, glioblastoma, lung carcinoma and breast cancer cells is inhibited. The action of disorazoles E1 and D1 is in this case cell cycle-dependent. Even in nanomolar concentrations the cell cycle is held in the G2/M phase and the cancer cells are forced into apoptosis.
WO 2004/024149 further shows that the antiproliferative action of disorazoles is based, inter alia, on an effective inhibition of tubulin polymerization. Further, disorazole E1 is active against paclitaxel- and vindesine-resistant cell lines. This matters in particular, since disorazole A1 is unsuitable for use as a cytostatic (Hoefle G, Annual Report 1999/2000 of the Gesellschaft für Biotechnologische Forschung (GBF), pages 101/103).
Wipf and co-workers examined the cellular activity of disorazole C and the structure-activity relationship of eight of its analogues (Wipf et al., Chem. Biol. Drug Des. 2006, 67(1): 66-73).
Total Synthesis strategies for the synthesis of disorazoles A1 and C1 have been studied and thoroughly described (Hillier M C et al., J. Org. Chem. 2001, 66: 6037-6045; Hartung I V et al., Organic Letters 2002, 4(19): 3239-3242; Wipf P et al., J. Am. Chem. Soc. 2004, 126(47): 15346-15347).
Disorazole A1 has also been further characterized: it was shown that it acts as an antimitotic agent on tubulin polymerization and induces apoptosis in mammalian cells (Elnakady Y A et al., Biochem. Pharmacol. 2004, 67(5): 927-935). Furthermore, methanolysis products of disorazole A1 have been generated and studied for potential anti-proliferative activity (Hearn B R et al., J. Nat. Prod. 2006, 69(1): 148-150).
The following prior art documents are directed to the biosynthesis of disorazoles or related compounds: WO 2004/053065 describes polynucleotides that code for disorazole polyketide synthase. Schupp and co-workers characterized a Sorangium cellulosum gene cluster for the biosynthesis of the macrolide antibiotic Soraphen A (Schupp T et al., Journal of Bacteriology 1995, 177: 3673-3679). Biosynthetic genes for the disorazole biosynthesis were also characterized by Carvalho R et al. (Carvalho R et al., Gene 2005, 359: 91-98), Kopp and coworkers (Kopp M et al., Chembiochem. 2005, 6(7): 1277-1286) and WO 2006/075013.
However, none of the aforementioned prior art documents disclose or suggest conjugates of disorazoles.
U.S. Pat. No. 6,214,969 describes luteinizing hormone releasing hormone (LHRH) analogues with cytotoxic moieties. Such moieties can be either D-/L-MeI (4-[bis(2-chloroethyl)amino]-D/L-phenylalanine), cyclopropanealkanoyl, aziridine-2-carbonyl, epoxyalkyl, 1,4-naphthoquinone-5-oxycarbonyl-ethyl, doxorubicinyl (Doxorubicin, DOX), mitomicinyl (Mitomycin C), esperamycinyl or methotrexoyl.
Disorazoles, however, which are tubulin polymerization inhibitors and induce apoptosis, are not mentioned nor is the use of them rendered obvious.
U.S. Pat. No. 5,843,903 is directed to cytotoxic anthracycline analogues, in particular doxorubicin (DOX) or its daunosamine modified derivatives. Such cytotoxic moieties are conjugated to peptide hormones, such as LHRH, bombesin and somatostatin and their analogues.
Schally and Nagy review novel therapeutic modalities for various cancers that consist of the use of targeted cytotoxic analogues of LHRH, bombesin and somatostatin which contain doxorubicin (DOX) or 2-pyrrolino-DOX (Schally A V et al., Life Sciences 2003, 72: 2305-2320; Nagy A et al., Current Pharmaceutical Design 2005, 11: 1167-1180).
In all three foregoing references disorazoles are not disclosed nor suggested.
Other prior art documents that deal with cytotoxic agent containing conjugates comprise antibody-cytotoxic agent conjugates for use in cancer therapy (Chen J et al., Expert Opin. Drug Deliv. 2005, 2(5): 873-890), antibody-drug conjugates for use in oncology (Hamann P R, Expert Opin. Drug Deliv. 2005, 15(9): 1087-1103), multi-class-anticancer-drug conjugates for use in tumor targeting (Jaracz S et al., Bioorganic & Medicinal Chemistry 2005, 13: 5043-5054), vinca alkaloid cytotoxic agent-oligopeptide conjugates for the treatment of prostate cancer and/or benign prostate hyperplasia (WO 97/12624, WO 98/10651 and WO 99/02175), prodrug vinblastine-peptidyl conjugates for the treatment of prostate cancer (Brady S F et al., J. Med. Chem. 2002, 45: 4706-4715), enzyme- and proton-activated prodrugs for selective anticancer therapies (Tietze L F et al., Current Pharmaceutical Design 2003, 9: 2155-2175) and prodrugs of natural anthracyclines for use in antibody-directed enzyme prodrug therapy (Michel S et al., Studies in Natural Products Chemistry 2000, 21: 157-180).
Again, in all these foregoing references, disorazoles, however, which are tubulin polymerization inhibitors and induce apoptosis, are not mentioned nor is the use of them suggested.